Doesn't work on Verizon phones - they are hoping to get it to work on it in a few months...
Most all of Verizon's phones now, at least the smartphones, Have radios for both domestic and international HSPA bands, and in the case of the new iPhone, LTE as well. Verizon also doesnt sim lock their phones. I recently went to Europe and used my Verizon phones with local sims without problems.
In fact, depending on where you go, you may want to look at 3(Three) UK's prepaid options. For ~$22/month (15GBP) you get 300 minutes, 3000 texts, and unlimited data which can be used in serveral countries around the world, including the US. If you're gonna be in one place for more than a few days at a time, data wise it may be cheaper if your in one of their covered countries.
http://www.three.co.uk/Discover/Phones/Feel_At_Home
